An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

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OR SCIENTIFIC METHOD. 289
tained. But in the homogeneous intermixture of effects
we have a more complicated task. There are several
causes, each producing a part of the effect, and we want
to know how much is due to each." It is true that the
Method of Residues is available in such cases within
the narrow limits in which it is available at all. Mill
himself admits that in most cases it cannot prove a
cause; it can only suggest
the search for one.
9. We may, therefore, sum up the characteristic
features of scientific Induction in the preliminary
stage :
(1) It is suggested or assumed, from previous observa
tions or by some other means, that A is the immediate
cause of a.
(2) Positive instances, of a occurring in connection
with A, are then sought for, experimentally if possible,
in order to establish the proposition
"
If A, then a"
(3) Negative instances, including apparent exceptions,
are then investigated in order to establish the proposition
"
If not A, then not a."
How far precisely do the Methods of Observation and
Experiment carry us ? The answer is, they cannot do
more than establish a causal law that a results from A
all circumstances ; and this only by the applica
tion of the most powerful method, that of Double
Difference, where both positive and negative instances
experimentally investigated. What more than this
do we want ? We want, if possible, to explain the law,
that is, to understand the
"
" how of it, the means by
which a always results from A. If we could bring this
law into harmony with other scientific laws, and more
especially if we could to any extent deduce it or antici
pate it on the ground of previous knowledge, we should
have passed from observation to explanation. The s